ASPECTS measures early ischemic changes on a non-contrast CT specifically within the middle cerebral artery territory. It looks at ten predefined brain regions, and each region showing signs of ischemia lowers the score by one, so a higher total means less established damage. This quick, regional assessment helps clinicians judge how much salvageable brain tissue remains and whether a patient with an acute ischemic stroke due to a large vessel occlusion in the anterior circulation is a good candidate for mechanical thrombectomy. In practice, a higher score suggests the patient is more likely to benefit from clot retrieval, while a very low score points to extensive established infarction where the risk/benefit of endovascular therapy is less favorable. While MCA involvement is the focus for this scoring, other territories (like PCA or vertebrobasilar) use different assessment patterns, and procedures like carotid endarterectomy or systemic thrombolysis are not guided by ASPECTS in the same way. Decompressive surgery is used for malignant edema in certain large infarcts and is not the decision point this scoring informs.